COLORED PAPER AND SUBSTRATES COATED FOR ENHANCED PRINTING PERFORMANCE

Abstract

Coated substrates are made from colored paper coated with a coating comprising silica or fumed metal oxide, such as precipitated silica, colloidal silica, fumed silica or fumed metal oxide. An opaque coating is formed which improves the L* and b* values of the colored paper. Images printed onto the paper show improved characteristics, such as a reduction in wick or bleed, or an improved color gamut.

Full Text

COLORED PAPER AND SUBSTRATES COATED FOR ENHANCED PRINTING
PERFORMANCE
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to United States Provisional Patent
Application Serial No. 60/777,394, filed on February 28, 2006, the entire contents of
which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] Substrates having improved printing properties are desirable in the art.;
SUMMARY
[0003] In one aspect, the invention may provide a coated substrate comprising a
colored paper coated with a coating comprising silica.
[0004] In another aspect, the invention may provide a coated substrate comprising
a colored paper coated with a fumed metal oxide.
[0005] In another aspect, the invention may provide a method of making a coated
substrate by applying a composition to a colored paper. The composition may comprise a
fumed metal oxide dispersion or a silica dispersion.
BRIEF DESCRIPTION OF THE FIGURES
[0006] FIGS. 1A and 1B are graphical representations depicting the L* and b*
values of kraft paper coated with various compositions comprising silica.

[0007] FIGS. 2A and 2B are graphical representations depicting the optical density
of black and colored inks printed onto kraft paper coated with various compositions
comprising silica.
[0008] FIG. 3 is a graphical representation depicting the static coefficient of
variation for paper coated with various compositions comprising silica.
[0009] FIGS. 4A and 4B are graphical representations depicting the color gamut of
paper coated with various compositions comprising silica.
DETAILED DESCRIPTION
[0010] The use of the terms "a" and "an" and "the" and similar referents in the
context of describing the invention (especially in the context of the following claims) are
to be construed to cover both the singular and the plural, unless otherwise indicated herein
or clearly contradicted by context. The terms "comprising," "having," "including," and
"containing" are to be construed as open-ended terms (i.e., meaning "including, but not
limited to,") unless otherwise noted. Recitation of ranges of values herein are merely
intended to serve as a shorthand method of referring individually to each separate value
falling within the range, unless otherwise indicated herein, and each separate value is
incorporated into the specification as if it were individually recited herein. All methods
described herein can be performed in any suitable order unless otherwise indicated herein
or otherwise clearly contradicted by context. The use of any and all examples, or

exemplary language (e.g., "such as") provided herein, is intended merely to better
illuminate the invention and does not pose a limitation on the scope of the invention unless
otherwise claimed. No language in the specification should be construed as indicating any
nonclaimed element as essential to the practice of the invention.
[0011] Preferred embodiments of this invention are described herein, including the
best mode known to the inventors for carrying out the invention. Variations of those
preferred embodiments may become apparent to those of ordinary skill in the art upon
reading the foregoing description. The inventors expect skilled artisans to employ such
variations as appropriate, and the inventors intend for the invention to be practiced
otherwise than as specifically described herein. Accordingly, this invention includes all
modifications and equivalents of the subject matter recited in the claims appended hereto
as permitted by applicable law. Moreover, any combination of the above-described
elements in all possible variations thereof is encompassed by the invention unless
otherwise indicated herein or otherwise clearly contradicted by context.
[0012] In one aspect, the invention provides a substrate coated with a coating
composition comprising silica. The silica may comprise at least one of fumed silica
particles, precipitated silica particles, gel silica particles, and combinations thereof. The
composition may further comprise a dispersing medium for the particles, such as water, a
binder or a combination thereof. The composition may be used to coat a substrate to
enhance the printing, such as ink jet printing, characteristics of the substrate.

[0013] Fumed silica particles, can be produced by pyrogenic processes and have
the chemical composition SiO2. Fumed silica particles, typically, are aggregate particles of
smaller primary particles, which are held together by relatively strong cohesive forces,
such that the aggregate particles are not broken down into primary particles when
dispersed in a liquid medium. Aggregate fumed silica particles may also form larger
agglomerate particles, which are held together by relatively weak cohesive forces.
Agglomerate particles may be broken down into aggregate particles when dispersed in a
liquid medium. Suitable fumed silica particles for use in the present invention have an
aggregate particle size of at least about 50, and more particularly, at least about 60, at least
about 70, at least about 75, at least about 80, at least about 90 or at least about 95 nm. The
aggregate particle size is generally less than about 400, and more particularly, less than
about 350, less than about 300, less than about 275, less than about 250, less than about
225, less than about 200, or less than about 190 nm.
[0014] The coating compositions may comprise fumed metal oxides, silica or
dispersions comprising the same. Commercially available fumed silicas suitable for use in
the invention include, but are not limited to, those sold under the trademark AERODISP®
(Degussa). Suitably, the fumed metal oxide in the dispersion may be doped with a
different fumed metal oxide, for example fumed silica doped with fumed alumina.
Suitable dispersions include, but are not limited to, AERODISP® WK 341 (a cationized
silica dispersion), VP Disp WK 7330 (a cationized fumed mixed metal oxide dispersion -
fumed silica doped with fumed alumina), AERODISP® WK 7520, AERODISP® G 1220,
AERODISP® W1450, AERODISP® W7215S, AERODISP® W 1226, AERODISP® W

SNOWTEX® C, SNOWTEX® N, SNOWTEX® O; and those commercially available
from Clariant / Rodel, such as KLEBOSOL® 30N25, KLEBOSOL® 30H25,
KLEBOSOL® 30N50PHN, KLEBOSOL® 30N50, KLEBOSOL® 30H50, KLEBOSOL®
1501-50, KLEBOSOL® 1508-50, KLEBOSOL® 1498-50. The coating compositions
may comprise any of these metal oxides, dispersions comprising metal oxides or
combinations thereof.
[0017] The surface area of most metal oxide particles can be determined by the
method of S. Brunauer, P. H. Emmet, and I. Teller, J. Am. Chemical Society, 60, 309
(1938), which is commonly referred to as the BET method. The fumed silica or fumed
metal oxide particles suitable for use in the invention have a BET surface area of at least
about 50, or at least about 70 m2/g, and less than about 400, less than about 350 or less
than about 325 m2/g. In some embodiments, the fumed silica particles have a BET surface
area of about 90 m2/g, about 200 m2/g or about 300 m2/g.
[0018] Gel silica and precipitated silica are formed by "wet chemistry" processes.
Like fumed silica, both gel silica and precipitated silica form a three-dimensional network
of particles or aggregates. The increased surface area provided by this three-dimensional
network permits gel silica and precipitated silica, when used to coat a surface, to
immobilize liquid in inks printed onto the surface, allowing for sharper images and a faster
ink drying time. Gel and precipitated silicas are therefore suitable for use in the coating
compositions.

[0019] Colloidal silica particles are generally produced by "wet chemistry"
processes and also have the chemical composition SiO2. Typically, colloidal silica is
produced by the addition of an acid to an alkaline metal silicate solution (e.g., sodium
silicate solution), thereby causing the silicate to polymerize and form discrete particles of
amorphous silica. Colloidal silica particles, typically, are discrete, substantially spherical
silica particles having no internal surface area. Commercially available colloidal silicas
include, but are not limited to, those sold under the trademarks LUDOX® (Grace Davison),
BINDZIL® (Akzo Nobel), and NYACOL™ (Akzo Nobel).
[0020] In one embodiment, the silica or fumed metal oxide is present in an aqueous
dispersion before being combined with a binder to form a composition and/or applied to
the substrate. The aqueous dispersion may comprise distilled or deionized water. The
composition also may comprise any number of suitable water-miscible liquids, such as one
or more water-miscible alcohols (e.g., methanol, ethanol, etc.) or ketones (e.g., acetone) in
addition to or instead of water.
[0021] As used herein, the term "binder" refers to a compound that helps facilitate
adherence of the silica or fumed metal oxide particles to the substrate. Any suitable
binder(s) can be used in the compositions including water swellable polymers having a
hydrophilic functional group such as a hydroxyl and/or amine. Suitably, the binder
comprises at least one of cellulose derivatives (e.g. hydroxyethyl cellulose, carboxymethyl
cellulose, cellulose esters, cellulose ethers), casein, gelatin, protein, starch (e.g. oxidized,
esterified, or other modified types of starch), vinyl polymers (e.g. polyvinyl alcohol,

polyvinyl pyrrolidine, polyvinyl acetate, styrene butadiene and derivatives), acrylic
polymers (e.g. polymethyl methacrylate, lattices of acrylic polymers, such as acrylate
esters, styrene-acrylic esters), polyesters, polycarbonate polymers, polyamides, polyimides,
epoxy polymers, phenolic polymers, polyolefins, polyurethanes copolymers thereof, and
mixtures thereof. In one embodiment, the binder is polyvinyl alcohol.
[0022] A suitable amount of binder in the composition depends on the particular
binder and upon the type of silica or fumed metal oxide used. For example, the optimum
amount of polyvinyl alcohol in the composition for a particular application may be
different from the optimum amount of polyvinyl pyrrolidine in the composition for that
application.
[0023] The ratio of silica or fumed metal oxide to binder in the composition may
also be varied depending upon the application and the desired result. Suitably, the ratio of
silica or fumed metal oxide to binder is at least about 0.25:1, at least about 1:1, at least
about 3:1, at least about 5:1, at least about 5.5:1, or at least about 6:1 and less than about
100:1, less than about 50:1, less than about 25:1, less than about 15:1, less than about 12:1,
less than about 10:1, less than about 7.5:1, or less than about 7:1.
[0024] Generally, the compositions may have a viscosity ranging from very low to
very high, so long as they are capable of being deposited on to the surface of the substrate
using techniques known in the art. Any suitable technique known in the art may be used to
measure the viscosity of the compositions. For example, viscosity may be measured using

a Brookfield LVT viscometer. Suitably, the viscosity may be at least about 1, at least
about 5, at least about 10, at least about 25, at least about 50, or at least about 100
centipoise and less than about 1,000, less than about 1,500, less than about 2,000, less than
about 2,500 or less than about 3,000 centipoise.
[0025] The composition can be prepared, using a variety of methods. In one
embodiment, the composition is prepared by combining an aqueous dispersion of silica or
a fumed metal oxide (e.g., an aqueous dispersion comprising fumed silica particles and
water) with at least one binder to produce the coating composition. The dispersion and the
binder may be combined, for example, by mixing with a high shear mixer. The pH of the
coating composition can be adjusted at any stage during its preparation to a desired pH.
However, in some embodiments no adjustment of the pH is required. In one embodiment,
the pH is directly adjusted on the dispersion when accompanied by high shear mixing. The
pH also may be adjusted after the dispersion is mixed with the binder (i.e., after forming
the coating composition). An adjustment in pH will usually be accompanied by a rise in
viscosity as the dispersion approaches the neutral pH range (6.5 - 7.5). The pH can be
adjusted using any suitable method, such as via the addition of an acid (e.g., mineral acid,
acidic cation exchange resin, etc.) or a base (e.g., an alkali metal hydroxide, basic anion
exchange resin, etc.). The coating compositions may be acidic or alkaline. Suitably, the pH
of the coating compositions may fall within a pH range of about 2.5 to about 10.5; for
example a pH range of about 2.5 to about 5 or about 8 to about 10.5.

[0027] In addition to these additives, the coating composition also can comprise a
mordant, such as a cationic polymer, which may enhance the water-fastness of the
composition. The cationic quaternary (NH4+) functionality of many polymers and salts may
facilitate the binding of anionic dyes commonly used in ink jet inks. Suitable mordants
include, but are not limited to, poly(vinylbenzyl trimethylamrnonium chloride),
polyamines, poly DADMAC (diallyl dimethyl ammonium chloride), polyethyleneimine
(PEI) and mixtures thereof.
[0028] Additionally, colorants such as pigments or dyes may be added that may
enhance the whiteness of the compositions when applied to a substrate. Suitable pigments
include clay (standard grades, calcined grades, delaminated grades, chemically structured
grades, composites/specialty grades), titanium dioxide (rutile, anatase), calcium carbonate
(ground, precipitated), alumina tri-hydrate and sodium silicates. Calcium carbonate,
alumina tri-hydrate and sodium silicates may also enhance the ink jet performance of the
composition when coated onto a substrate and enhance anti-slip properties. The presence
of silica or fumed metal oxide in the composition, such as fumed silica, may
advantageously reduce the amount of agglomeration of these additional pigments.
[0029] The invention further provides a recording medium comprising a substrate
coated with the composition as described herein (e.g., a composition comprising a binder
and an aqueous dispersion comprising fumed silica particles and water) applied to at least a
portion of the substrate. The substrate is suitably a paper that can be used as a packaging
material, such as colored paper. As used herein, the term "paper" includes, but is not

limited to paper, paperboard and cardboard. As used herein, the term "colored paper"
means paper that is made from unbleached cellulose fibers, or paper that is made from
bleached cellulose fibers, but has had color added such as by incorporating a colorant, such
as a dye or pigment, into or onto the paper. "Bleached cellulose fibers" are cellulose fibers
that have been treated by contacting the fibers with a bleaching agent, such as chorine-
based bleaches (chlorine dioxide, perchlorate) and/or peroxides. In one embodiment, the
paper may be made from unbleached cellulose fibers. In another embodiment, the paper is
made from bleached cellulose fibers and comprises a colorant, such as a dye or pigment.
Suitably, the substrate may be paper used in packaging materials such as boxes, sacks,
bags and the like. In one embodiment, the substrate is brown kraft liner paper. Suitable
papers include those having a GE brightness of less than about 90%, less than about 88%,
less than about 86%, less than about 84%, less than about 82% less than about 80%, less
than about 75%, less than about 70%, less than about 65% or less than about 60%, and
those having a GE brightness of at least about 5%, at least about 10%, at least about 15%,
at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least
about 40%, at least about 45%, at least about 50%, or at least about 55%.
[0030] The inventor surprisingly and unexpectedly discovered that, in contrast to
the transparent or translucent layers formed when silica coatings are applied to photo
papers, the application of coating compositions disclosed herein to colored paper caused
the paper to have a whiter, brighter surface. Moreover, the compositions produced a
uniform opaque layer when applied to the surface of the substrate.

[0031] Whiteness of a substrate such as paper can be estimated using an L* value,
which is a measure of the total amount of light reflected off the surface of the substrate. A
higher L* value correlates with increased whiteness. Suitably, the coating compositions

may improve the L* whiteness value of a substrate by at least about 2, at least about 3, at
least about 4, at least about 5, at least about 6, at least about 7, at least about 8, at least
about 9, or at least about 10. The blue-yellow hue of paper is estimated using b* values.
A lower b* value indicates that the substrate has a less yellow and more blue hue. Blue is
perceived by the eye as being closer to white, and lower b* values are desirable. The
coating compositions may reduce the b* value of the surface. Suitably, the coating
compositions reduce the b* value of the substrate by at least about 2, at least about 3, at
least about 4, at least about 5, at least about 6, at least about 7, at least about 8, at least
about 9, at least about 10, at least about 11 or at least about 12.
[0032] The recording medium described herein can be prepared by a method
comprising (a) providing a substrate; (b) coating at least a portion of the substrate with the
composition described herein (e.g., a composition comprising at least one binder and an
aqueous dispersion comprising fumed silica or fumed metal oxide particles) to provide a
coated substrate; and (c) optionally drying the composition on the substrate. Furthermore,
the composition may be repeatedly applied to the substrate to provide a recording medium
having a coating with a desired thickness.
[0033] Any suitable method can be used to coat a portion of the substrate, directly
or indirectly, with the composition. Suitable methods include, but are not limited to, roll

coating, blade coating, air knife coating, rod coating (e.g., using a Meyer rod or the like),
bar coating, cast coating, gate roll coating, wire bar coating, short-dowel coating, slide
hopper coating, curtain coating, flexographic coating, gravure coating, Komma coating,
size press coating in the manner of on- or off-machine, and die coating. Rapid,
inexpensive methods such as rod coating and blade coating may be particularly suitable.
The coating applied to the substrate can be of any suitable thickness. The coating is
suitably applied to provide at least about 0.S, at least about 1, at least about 2, at least about
3, at least about 4, at least about 5, at least about 6, or at least about 7 g silica or fumed
metal oxide per m2 of substrate, and less than about 30, less than about 25, less than about
20, less than about 15, less than about 14, less than about 13, less than about 12, less than
about 11, less than about 10, less than about 9, or less than about 8 g silica or fumed metal
oxide per m2 of substrate. The amount of silica or fumed metal oxide per m2 of substrate,
is referred to herein as the "coat weight."
[0034] After application of the coating composition to the substrate, the coated
substrate can be dried using any suitable method or combination of methods to provide the
recording medium. Suitable drying methods include, but are not limited to, air or
convection drying (e.g., linear tunnel drying, arch drying, air-loop drying, sine curve air
float drying, etc.), contact or conduction drying, and radiant-energy drying (e.g., infrared
drying and microwave drying).
[0035] An image may be printed, directly or indirectly, onto the recording medium
using one or more of a variety of printing techniques, including gravure (flexo, roto), offset

litho, electrophotographic, and high speed digital (for example, using XEIKON™ printers
or INDIGO™ printers) techniques. The recording medium is particularly suited to receive
an image from an ink jet printer. Images made using an ink jet printer on a recording
medium comprising the coating compositions are brighter, sharper and have a higher
resolution compared with a comparable substrate that has not been coated with the coating
compositions. For example, inks ink-jet printed on a substrate coated with a coating
composition described herein, compared with inks printed onto a comparable uncoated
substrate, may show a reduction in bleeding and wicking of the ink of at least about 5
microns, at least about 10 microns, at least about 15 microns, at least about 20 microns, at
least about 25 microns, or about at least 30 microns. Inks ink-jet printed on a substrate
coated with a coating composition, compared with inks printed onto a comparable
uncoated substrate, may show an improvement in the raggedness of a line ink-jet printed
onto the coated surface, such that the amount of line raggedness is reduced by at least
about 2 microns, at least about 5 microns, at least about 10 microns, at least about 15
microns, at least about 20 microns, or at least about 25 microns. The brightness of images
printed on a substrate coated with the coating compositions described herein may also be
improved over a comparable uncoated substrate. For example, the optical density of inks
printed onto a substrate coated with a coating composition, compared with inks printed in a
comparable manner onto a comparable uncoated substrate, may be raised by at least about
0.05, at least about 0.1, at least about 0.15, at least about 0.2 or at least about 0.25.
[0036] The coating compositions may also improve the color gamut of the
substrate. The color gamut of a substrate is the number of colors that can be accurately

represented under a certain set of conditions. The compositions may improve the color
gamut of a substrate by at least about 50%, at least about 75%, at least about 100%, at least
about 150%, at least about 200%, at least about 300%, or at least about 400%.
[0037] Coating compositions comprising one or more fumed metal oxides or
silicas, for example fumed silica, may also improve or enhance the anti-slip properties of
the substrate by increasing the coefficient of friction of the substrate. As used herein, the
coefficient of friction means the static coefficient of friction. The coefficient of friction
can be suitably measured by any technique known in the art. For example, a technique
known in the art to measure the static coefficient of friction is a TAPPI method T815 om-
01. Suitably, the coating compositions increase the coefficient of friction of the substrate
by at least about 0.2, at least about 0.25, at least about 0.3, at least about 0.35, at least
about 0.4, at least about 0.45, or at least about 0.5. Suitably, the silica or fumed metal
oxide in the coating increases the coefficient of friction of the substrate by at least about
0.2, at least about 0.25, at least about 0.3, at least about 0.35, or at least about 0.4
compared with the same substrate coated with a similar coating not comprising silica or
fumed metal oxide.
[0038] The following examples further illustrate the invention but should not be
construed as in any way limiting its scope.
EXAMPLE 1
Composition Comprising an Alkaline Fumed Silica (Particle Size 100 nm) Dispersion

[0039] AERODISP® W7622 (a low viscosity, slightly alkaline, water-based
dispersion of AEROSIL® (fumed silica having a particle size of 100 nm and a surface area
of 300 m2/g)) was combined with CELVOL® 523 (polyvinyl alcohol) using a
DISPERMAT® mixer with a high shear blade at a shear rate of 1200 inverse minutes. The
proportions of AERODISP® and CELVOL® 523 were chosen such that the weight ratio of
fumed silica to polyvinyl alcohol in the composition was 6.67:1.
EXAMPLE 2
Composition Comprising an Alkaline Fumed Silica (Particle Size 120 nm) Dispersion
[0040] AERODISP® W7520 (a low viscosity, slightly alkaline, water-based
dispersion of AEROSIL® (fumed silica having a particle size of 120 nm and a surface area
of 200 m2/g)) was combined with CELVOL® 523 (polyvinyl alcohol) using a
DISPERMAT® mixer with a high shear blade at a shear rate of 1200 inverse minutes. The
proportions of AERODISP® and CELVOL® 523 were chosen such that the weight ratio of
fumed silica to polyvinyl alcohol in the composition was 6.67:1.
EXAMPLE 3
Composition Comprising an Acidic Fumed Silica (Particle Size 180 nm) Dispersion
[0041] AERODISP® W7215 S (a low viscosity, slightly acidic, water-based
dispersion of AEROSIL® (fumed silica having a particle size of 180 nm and a surface area
of 90 m2/g)) was combined with CELVOL® 523 (polyvinyl alcohol) using a
DISPERMAT® mixer with a high shear blade at a shear rate of 1200 inverse minutes. The

proportions of AERODISP® and CELVOL® 523 were chosen such that the weight ratio of
fumed silica to polyvinyl alcohol in the composition was 6.67:1.
EXAMPLE 4
Compositions Comprising Colloidal Silica Dispersions
[0042] Five different compositions were made by combining CELVOL® 523
(polyvinyl alcohol) with one of the following five colloidal silica dispersions: IJ935
(obtained from Azko Nobel); NYACOL™ 1430 (obtained from Nyacol Nanotechnologies,
Inc.), BINDZIL™ 30/60 (obtained from Azko Nobel); LUDOX™ HS40 (obtained from
Grace Division); LUDOX™ SM30 (obtained from Grace Division). The proportions of
polyvinyl alcohol and colloidal silica were chosen such that the weight ratio of colloidal
silica to polyvinyl alcohol in each composition was 6.67:1. The colloidal silica was
combined with the polyvinyl alcohol using a DISPERMAT® mixer with a high shear
blade, at a shear rate of 1200 inverse minutes
EXAMPLE 5
Composition Comprising a Precipitated Silica Dispersion
[0043] SIPERNAT® 22 S, a fine particle precipitated silica with a high absorption
capacity for liquids, was combined with CELVOL® 523 (polyvinyl alcohol) using a
DISPERMAT® mixer with a high shear blade at a shear rate of 1200 inverse minutes. The
proportions of SIPERNAT® 22 S and CELVOL® 523 were chosen such that the weight
ratio of precipitated silica to polyvinyl alcohol in the composition was 6.67:1.

EXAMPLE 6
Application of the Composition of Example 1 to Brown Kraft Liner Paper
[0044] The composition of Example 1 was used to coat brown kraft liner paper
(75#) using a #5 or #15 wire rod, such that the amount of fumed silica dispersed over the
surface of the paper was 8.6 g/m2 or 13.3 g/m2. L*, a* and b* values for the coated paper
compared with the uncoated paper are presented in Table 1. At 13.3 g/m2, the paper coated
with silica had a b* value of 2.05 and an L*value of 68.71, compared with a b* value of
10.55 and an L* value of 61.94 for uncoated paper, and a b* value of 12.23 and an L*
value of 56.68 for paper coated with CELVOL® 523 (polyvinyl alcohol) but no silica. The
L* and b* values for paper for uncoated paper, paper coated with polyvinyl alcohol but no
silica (CELVOL® 523), and the paper coated with 13.3 g/m2 of the composition of
Example 1 (W7622) are also represented graphically in Figure 1 (A and B).
[0045] The lower b* value of the paper coated with fumed silica indicated that the
silica coating had imparted a less yellow and more blue hue to the kraft paper. The coated
paper was also visually significantly whiter than the uncoated paper. The results for the
L*, a* and b* values (measured in triplicate) of the coated paper are shown in Table 1.

EXAMPLE 7
Application of the Composition of Example 2 to Brown Kraft Liner Paper
[0046] The composition of Example 2 was used to coat brown kraft liner paper,
using a #5 or #15 wire rod, such that the amount of fumed silica dispersed over the surface
of the paper was 8.0 g/m2 or 11.7 g/m2. The L*, a* and b* values for the coated paper
compared with the uncoated paper are presented in Table 2. At 11.7 g/m2, the coated paper
had a b* value of 2.22 and an L* value of 69.45, compared with a b* value of 10.55 and an
L* value of 61.94 for uncoated paper, and a b* value of 12.23 and an L* value of 56.68 for
paper coated with CELVOL® 523 (polyvinyl alcohol) but no silica. The L* and b* values
for paper for uncoated paper, paper coated with polyvinyl alcohol but no silica (CELVOL®
523), and the paper coated with 111.7 g/m2 of the composition of Example 2 (W7520) are
also represented graphically in Figure 1 (A and B).
[0047] The lower b* value of the paper coated with fumed silica indicated that the
silica coating had imparted a less yellow and more blue hue to the kraft paper. The coated
paper was also visually significantly whiter than the uncoated paper. The results for the
L*, a* and b* values (measured in triplicate) of the coated paper are shown in Table 2.

EXAMPLE 8
Application of the Composition of Example 3 to Brown Kraft Liner Paper
[0048] The composition of Example 3 was used to coat brown kraft liner paper,
using a #5 or #15 wire rod, such that the amount of fumed silica dispersed over the surface
of the paper was 8.5 g/m2 or 10.7 g/m2. The L*, a* and b* values for the coated paper
compared with the uncoated paper are presented in Table 3. At 10.7 g/m2, the coated paper
had a b* value of 2.05 and an L* value of 68.71, compared with a b* value of 10.55 and an
L* value of 61.94 for uncoated paper, and a b* value of 12.23 and an L* value of 56.68 for
paper coated with CELVOL® 523 (polyvinyl alcohol) but no silica. The L* and b* values
for paper for uncoated paper, paper coated with polyvinyl alcohol but no silica (CELVOL®
523), and the paper coated with 10.7 g/m2 of the composition of Example 3 (W7215 S) are
also represented graphically in Figure 1 (A and B).
[0049] The lower b* value of the paper coated with fumed silica indicated that the
silica coating had imparted a less yellow and more blue hue to the kraft paper. The coated
paper was also visually significantly whiter than the uncoated paper. The results for the
L*, a* and b* values (measured in triplicate) of the coated paper are shown in Table 3.

Application of Compositions of Example 4 to Brown Kraft Liner Paper
[0050] The compositions of Example 4 were used to coat brown kraft liner paper
using a #5 or #15 wire rod. Values were averaged from paper coated with LUDOX®
HS40, LUDOX® SM30 or NYACOL® 1450. The average coat weight of these three
coatings was 9.4 g/m2, with an average b* value of 11.23 and an average L* value of
61.36, compared with a b* value of 12.23 and an L* value of 56.68 for paper coated with
CELVOL® 523 (polyvinyl alcohol) but no silica, and a b* value of 10.55 and an L* value
of 61.94 for uncoated paper.
[0051] The colloidal silica compositions did not significantly lower the b* value of
the coated paper. The paper coated with colloidal silica also was not visually significantly
whiter than the uncoated paper or paper coated with CELVOL® 523 (polyvinyl alcohol)
but no silica.
[0052] Results of the L*, b* and a* values (measured in triplicate) for paper coated
with the compositions of Example 4 comprising IJ935 (obtained from Azko Nobel);
NYACOL™ 1430 (obtained from Nyacol Nanotechnologies, Inc.), LUDOX™ HS40
(obtained from Grace Division); or LUDOX™ SM30 (obtained from Grace Division) are
presented in Tables 4-7.

[0053] The L* and b* values for paper for uncoated paper, paper coated with
polyvinyl alcohol but no silica (CELVOL® 523), and the paper coated with 9.4 g/m2 of
colloidal silica (values averaged from LUDOX® HS40, LUDOX® SM30, and NYACOL®
1450) are also represented graphically in Figure 1 (A and B).

EXAMPLE 10
Application of the Composition of Example 5 to Brown Kraft Liner Paper
[0054] The composition of Example 5 was used to coat brown kraft liner paper,
using a #15 wire rod, such that the amount of fumed silica dispersed over the surface of the
paper was 11.1 g/m2. The L*, a* and b* values for the coated paper compared with the
uncoated paper are presented in Table 8. At 11.1 g/m2, the coated paper had a b* value of-
0.95 and an L* value of 71.02, compared with a b* value of 10.55 and an L* value of
61.94 for uncoated paper, and a b* value of 12.23 and an L* value of 56.68 for paper
coated with CELVOL® 523 (polyvinyl alcohol) but no silica. The L* and b* values for
paper for uncoated paper, paper coated with polyvinyl alcohol but no silica (CELVOL®
523), and the paper coated with 11.1 g/m2 of the composition of Example 5 (SIPERNAT®
22 S) are also represented graphically in Figure 1 (A and B).
[0055] The lower b* value of the paper coated with precipitated silica indicated
that the silica coating had imparted a less yellow and more blue hue to the kraft paper. The
coated paper was also visually significantly whiter than the uncoated paper. The results for
the L*, a* and b* values (measured in triplicate) of the coated paper are shown in Table 8.

[0061] Ink (either cyan, magenta, yellow, black, red, green or blue) was ink jet
printed onto brown kraft liner paper (75#) coated with the composition of Example 1 at a
coat weight of either 8.00 or 11.71 g silica per m2 paper using an Epson Stylus Photo R200
printer and using the following settings: Glossy Photo/Best Photo/EnhanceAJnidirectional.
[0062] The optical density (OD), L*, a* and b* values were measured in triplicate
for the cyan, magenta, yellow, and black, inks and the L*, a* and b* values were measured
in triplicate for the red, green and blue inks. The results are presented in Tables 11 and 12.

[0063] The optical density averages for black, cyan, magenta and yellow inks
printed onto paper coated with 13.3 g/m2 of the composition of Example 1 (W7622) are
also represented graphically in Figure 2 (A and B).
EXAMPLE 14
Images Printed on Kraft Liner Paper Coated with Composition of Example 2
[0064] Ink (either cyan, magenta, yellow, black, red, green or blue) was ink jet
printed onto brown kraft liner paper (75#) coated with the composition of Example 2 at a
coat weight of either 8.00 or 11.71 g silica per m2 paper using an Epson Stylus Photo R200
printer and using the following settings: Glossy Photo/Best Photo/Enhance/Unidirectional.
[0065] The optical density (OD), L*, a* and b* values were measured in triplicate
for the cyan, magenta, yellow, and black, inks and the L*, a* and b* values were measured
in triplicate for the red, green and blue inks. The results are presented in Tables 13 and 14.

[0066] The optical density averages for black, cyan, magenta and yellow inks
printed onto paper coated with 11.7 g/m2 of the composition of Example 2 (W7520) are
also represented graphically in Figure 2 (A and B).
EXAMPLE 15
Images Printed on Kraft Liner Paper Coated with Composition of Example 3
[0067] Ink (either cyan, magenta, yellow, black, red, green or blue) was ink jet
printed onto brown kraft liner paper (75#) coated with the composition of Example 3, at a
coat weight of either 8.5 or 10.7 g silica per m2 paper, using an Epson Stylus Photo R200
printer and using the following settings: Glossy Photo/Best Photo/Enhance/Unidirectional.
[0068] The optical density (OD), L*, a* and b* values were measured in triplicate
for the cyan, magenta, yellow, and black, inks and the L*, a* and b* values were measured
in triplicate for the red, green and blue inks. The results are presented in Tables 15 and 16.

[0074] The optical density (OD), L*, a* and b* values were measured in triplicate
for the cyan, magenta, yellow, black, red, green and blue inks. The results are presented in
Table 22.

EXAMPLE 18
Color Gamut of Kraft Paper Coated with Compositions of Examples 1-5
[0075] The color gamut was measured for uncoated kraft liners, kraft liners coated
only with polyvinyl alcohol and kraft liners coated with the compositions of Examples 1-5,
as described in Examples 6-10. Values for the color gamut are shown in Tables 9-22. The
results are shown in Figure 4 (A and B). Each of the coating compositions comprising
fumed silica or precipitated silica substantially increased the color gamut of the kraft liner
paper by approximately four-fold when compared with uncoated kraft liner paper, or kraft

liner paper coated with polyvinyl alcohol (Figure 4 A). In contrast, the coating
compositions comprising colloidal silica did not increase the color gamut of the kraft liner
paper, or increased the color gamut only slightly when compared with uncoated kraft liner
paper, or kraft liner paper coated with polyvinyl alcohol. (Figure 4 B).
EXAMPLE 19
Coefficient of Friction of Kraft Paper Coated with Polyvinyl Alcohol and Silica
[0076] The pick up (the amount of coating dried onto the paper over a defined area)
and coefficient of friction for brown kraft paper coated with compositions comprising
silica was measured. Kraft liner paper (75#) (obtained from Uline) was coated using a #5
wire wound rod. The sheet was first blow dried, then dried under restraint. The pick-up
was calculated gravimetrically when the paper was completely dry. The samples were
mounted on the Coefficient of Friction Tester (TMI model 32-25) and tested per TAPPI
method T815 om-01 with a 200g sled with an area of 2.5 x 2.5".
[0077] The pick-up and coefficient of friction for paper coated with one of three
different types of polyvinyl alcohol (CELVOL® 523, CELVOL® 603 or CELVOL® 08-
125) are shown in Table 23. The pick-up and coefficient of friction for paper coated with
CELVOL® 523 and one of the following fumed silicas: W7330, W7520, W7622, W7215S,
W1226; precipitated silica SIPERNAT® 22 S (22 S); or one of the following colloidal
silicas: IJ935, N1430, BZ 30/60, HS40, SM30 are shown in Table 24. The numbers in
parentheses in Table 23 reflect the ratio of silica to polyvinyl alcohol in each composition.
The average for three separate samples, each measured five times is provided in Tables 23

liner paper coated with polyvinyl alcohol (Figure 4 A). In contrast, the coating
compositions comprising colloidal silica did not increase the color gamut of the kraft liner
paper, or increased the color gamut only slightly when compared with uncoated kraft liner
paper, or kraft liner paper coated with polyvinyl alcohol. (Figure 4 B).
EXAMPLE 19
Coefficient of Friction of Kraft Paper Coated with Polyvinyl Alcohol and Silica
[0076] The pick up (the amount of coating dried onto the paper over a defined area)
and coefficient of friction for brown kraft paper coated with compositions comprising
silica was measured. Kraft liner paper (75#) (obtained from Uline) was coated using a #5
wire wound rod. The sheet was first blow dried, then dried under restraint. The pick-up
was calculated gravimetrically when the paper was completely dry. The samples were
mounted on the Coefficient of Friction Tester (TMI model 32-25) and tested per TAPPI
method T815 om-01 with a 200g sled with an area of 2.5 x 2.5".
[0077] The pick-up and coefficient of friction for paper coated with one of three
different types of polyvinyl alcohol (CELVOL® 523, CELVOL® 603 or CELVOL® 08-
125) are shown in Table 23. The pick-up and coefficient of friction for paper coated with
CELVOL® 523 and one of the following fumed silicas: W7330, W7520, W7622, W7215S,
W1226; precipitated silica SIPERNAT® 22 S (22 S); or one of the following colloidal
silicas: IJ935, N1430, BZ 30/60, HS40, SM30 are shown in Table 24. The numbers in
parentheses in Table 23 reflect the ratio of silica to polyvinyl alcohol in each composition.
The average for three separate samples, each measured five times is provided in Tables 23

and 24. For each coating, the standard deviation of the measurements fell between 0.02
and 0.04 (2 d.p.) for the coefficient of friction and between 0.06 and 2.98 (2 d.p.) for the
pick up.
[0078] Visual inspection of paper coated with the compositions recited in Table 24
revealed that each fumed silica or precipitated silica composition coated the paper with an
opaque and uniform layer, making the paper appear whiter and brighter. In contrast,
papers coated with each of the colloidal silicas essentially remained translucent and were
comparable to the paper coated only with polyvinyl alcohol.

[0079] All patents, publications and references cited herein are hereby fully
incorporated by reference. In case of conflict between the present disclosure and
incorporated patents, publications and references, the present disclosure should control.

WE CLAIM:
1.A coated substrate comprising a colored paper that is made from
unbleached cellulose fibers, or paper that is made from bleached
cellulose fibers, but has had color added into or onto the paper,
characterized in that it is coated with a coating comprising fumed silica
and a binder, wherein the fumed silica has an aggregate particle size of
at least 50 and less than 400 nm, the binder comprises polyvinyl alcohol,
and the coating further comprises poly (diallyl dimethyl ammonium
chloride).
2.The coated substrate as claimed in claim 1, wherein the colored paper
has a GE brightness of less than about 90%.
3.The coated substrate as claimed in claims 1 or 2, wherein the colored
paper comprises unbleached cellulose fibers.
4.The coated substrate as claimed in any one of claims 1 to 3, wherein
the colored paper comprises kraft paper.
5.The coated substrate as claimed in any one of claims 1 to 4, wherein in
the coating the silica to binder ratio is at least about 0.25:1.

6.The coated substrate as claimed in any one of claims 1 to 5, wherein
the coating has a coat weight of less than about 15g silica per m2
substrate.
7.The coated substrate as claimed in any one of claims 1 to 6, wherein
the coated substrate is incorporated into a packaging material selected
from a box, sack and bag.
8.The coated substrate as claimed in claim 7, wherein it further
comprises an image printed on the coated substrate.
9.The coated substrate as claimed in claim 8, wherein the image is
formed by an inkjet printer.
10.A method of making a coated substrate as defined in claims 1 to 9,
characterized in applying a composition comprising an aqueous
dispersion of fumed silica and a binder, wherein the fumed silica has an
aggregate particle size of at least 50 and less than 400 nm, the binder
comprises polyvinyl alcohol, and the coating further comprises poly
(diallyl dimethyl ammonium chloride), to a colored paper.

Title: COLORED PAPER AND SUBSTRATES COATED
FOR ENHANCED PRINTING PERFORMANCE
Coated substrates are made from colored paper coated with a coating comprising
silica or fumed metal oxide, such as precipitated silica, colloidal silica, fumed
silica or fumed metal oxide. An opaque coating is formed which improves the
L* and b* values of the colored paper. Images printed onto the paper show
improved characteristics, such as a reduction in wick or bleed, or an improved
color gamut.